Safety device for an exposure lamp in a reproduction apparatus

ABSTRACT

A safety device wherein an exposure lamp is put out without failure even in the case where the exposure lamp is kept on because of some trouble in the switching-off circuit after finishing an exposure.

United States Patent [72 Inventors TakeshiUkai [50] FieldofSearch.........,.... .........v................... 315/241 Tokyo; ,141.4,14l.8,157;317/36,

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[54] SAFETY DEVICE IF UR AN EXPOSURE LAMP IN A REPRODUCTIION APPARATUS 7 Ciaims, 1 Drawing Fig.

ABSTRACT: A safety device wherein an exposure lamp is put 307/1413 out without failure even in the case where the exposure lamp 307/94, 315/241 Witching-off circuit is kept on because of some trouble in the s 1101b 3/34- after finishing an exposure.

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Print Button Reproductwn Cycle Controller PAT'ENTED mes |97l 3.571.612

Reproduction Cycle Controller SAFETY DEVICE FOR AN EXPOSURE LAMP IN A REPRODUCTHON AEPARATUS The present invention relates to a reproduction apparatus, and more specifically, to a safety device for an exposure lamp in an electrophotographic reproduction apparatus.

An exposure lamp for an elctrophotographic reproduction apparatus is lighted by pushing an operation button, and put out after the finish of an exposure in a normal state. However, in the case where the exposure lamp continues to light after the finish of the exposure because of some trouble in the switching-off circuit, the reproduction apparatus becomes unusable, and moreover, it results in the waste of electric power and a possible outbreak of fire.

The invention provides a safety device which switches off exposure lamp without failure in the case where the exposure lamp continues to light after the finish of an exposure because of some trouble in the switching-off circuit.

The following is an explanation of an embodiment of the invention in conjunction with the accompanying drawing, wherein:

The single FIG. denotes a circuit indicating an embodiment of the safety device made in accordance with the invention.

in the HO, an exposure lamp 2 and a relay contact 4 mounted in a relay coil 3 are connected in series to the main circuit closed through a switch 1. in the relay contact 4, NC denotes a normally closed contact at 3b NO denotes a normally opened contact at Sat. An exposure control means 5 completes the circuit in accordance with an external exposure signal and energizes the relay coil. in this circuit, there is provided a safety contact 6 in accordance with the present invention, which is mounted to a relay coil 7. A switching transistor 6 is connected in series to the relay coil 7. A switching transistor 6 is connected in series to the relay coil 7. A discharge resistor 9, a charging current control resistor 10 and a charge and discharge condenser 11 are connected to the base side of the transistor 8. The reference number 12 denotes a diode for preventing reverse voltage, 13 denotes a Zener diode and resistor for constant voltage, and 14 denotes a rectitier means.

The operation of the above-mentioned circuit is as follows:

When the switch 1 of the main circuit is closed, a voltage is applied between a collector and an emitter of the transistor 8. Simultaneously, the charge and discharge condenser 11 is charged through the normally closed contact of the relay contact 4 and the charging current suppressing resistor 10. In this time, further, a current begins to flow from the base of the transistor 8 through the discharge resistor 9. Therefore, the switching transistor 8 becomes conductive, a current flows through the relay coil 7 to energize it, and the contact 6 is accordingly closed.

in this state, when an external exposure signal is applied to the exposure control means 5 the circuit of the relay coil 3 is closed, and a current flows in said circuit to energize the relay coil 3. Therefore, the normally closed contact of the contact 4 provided at the relay coil 3 is opened while the normally opened contact is closed, the circuit for the exposure lamp 2 is closed, and the lamp 2 is lighted. When an external exposure release signal is applied to the exposure control means 5, said exposure control means 5 opens the circuit for the relay coil 3 in order to stop the energization of the relay coil 3, the normally opened contact of the relay contact 4 is opened to cut off the circuit of the exposure lamp 2, and the exposure lamp 2 is switched off.

As described above, when the relay coil 3 is energized, the normally closed contact of the relay 4 is opened and thereby the circuit for charging the charge and discharge condenser 11 is opened. Said condenser 11 then begins to discharge through the discharge resistor 9 and the switching transistor 8. After a predetermined time, when this discharge current, that is, the current from the base of the transistor 8 decreases to a value less than a predetermined one, the collector current also decreases and the energization of the relay coil is stopped.

Therefore, the safety contact 6 is opened.

In the case where the switching-off circuit for the exposure lamp 2 is in a normal state, the time constants of the condenser 11 and the resistor 9 are selected so that an external exposure release signal may be given to the exposure control means 5 earlier than the contact 6 is opened through the deenergization of the relay coil 7. However, in the case where the exposure lamp 2 continues to light in spite of the external signal because some trouble in the switching-off circuit, for example, in the exposure control means 5, the contact 6 is operated through the relay coil 7 in order to stop the energization of the relay coil 3, the circuit of the exposure lamp 2 is opened, and the lamp is switched off.

According to the safety device of the invention, even if the switching-off circuit of the exposure lamp becomes inoperable, the lamp is reliably switched off. So the normal function of the reproduction apparatus is maintained, and the waste of electric energy and the possible outbreak of fire are prevented. Moreover, since the charging circuit of the safety device of the present invention is opened directly through the on-off relay for the exposure lamp, the construction of the present invention is relatively simple and the operation thereof is reliable.

While the present invention has been particularly described in terms of a specific embodiment thereof, it will be understood that in view of the foregoing specification numerous deviations therefrom and modifications thereupon may be readily devised by those skilled in the art without departing from the spirit of the present invention.

We claim:

1. A safety device for an exposure lamp in a reproduction apparatus, said safety device comprising a relay coil and a relay contact adapted to be electrically coupled with said exposure lamp, said relay contact including normally open and normally closed terminals, exposure control means electrically coupled with said relay coil and adapted for being electrically coupled with an external power source, a safety relay coil and a safety relay contact electrically coupled with said exposure control means, a switching transistor electrically coupled with said safety relay coil and said safety relay contact, and a condenser electrically coupled with said switching transistor and said safety relay contact.

2. A safety device as claimed in claim 1, wherein said exposure control means and said safety relay contact are connected in series.

3. A safety device as claimed in claim 2, wherein said lamp and one terminal of said normally open terminals of said relay contact adapted to be are connected in series.

4. A safety device as claimed in claim 3, wherein said condenser and said normally closed terminals of said relay contact are connected in series.

5. A safety device as claimed in claim 4, including a discharge resistor interconnecting said condenser with the base of said transistor.

6. A safety device as claimed in claim 5, including a charging resistor interconnecting said condenser with one terminal of said normally closed terminals'of said relay contact.

7. A safety device as claimed in claim 6, wherein said safety relay coil is connected to the collector electrode of said transistor. 

1. A safety device for an exposure lamp in a reproduction apparatus, said safety device comprising a relay coil and a relay contact adapted to be electrically coupled with said exposure lamp, said relay contact including normally open and normally closed terminals, exposure control means electrically coupled with said relay coil and adapted for being electrically coupled with an external power source, a safety relay coil and a safety relay contact electrically coupled with said exposure control means, a switching transistor electrically coupled with said safety relay coil and said safety relay contact, and a condenser electrically coupled with said switching transistor and said safety relay contact.
 2. A safety device as claimed in claim 1, wherein said exposure control means and said safety relay contact are connected in series.
 3. A safety device as claimed in claim 2, wherein said lamp and one terminal of said normally open terminals of said relay contact adapted to be are connected in series.
 4. A safety device as claimed in claim 3, wherein said condenser and said normally closed terminals of said relay contact are connected in series.
 5. A safety device as claimed in claim 4, including a discharge resistor interconnecting said condenser with the base of said transistor.
 6. A safety device as claimed in claim 5, including a charging resistor interconnecting said condenser with one terminal of said normally closed terminals of said relay contact.
 7. A safety device as claimed in claim 6, wherein said safety relay coil is connected to the collector electrode of said transistor. 